[all-commits] [llvm/llvm-project] bf6357: [Transforms] LoopIdiomRecognize recognize strlen a...

[Henry Jiang via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: bf6357f0f51eccc48b92a130afb51c0280d56180
      https://github.com/llvm/llvm-project/commit/bf6357f0f51eccc48b92a130afb51c0280d56180
  Author: Henry Jiang <h243jian at uwaterloo.ca>
  Date:   2025-03-14 (Fri, 14 Mar 2025)

  Changed paths:
    M llvm/include/llvm/Transforms/Scalar/LoopIdiomRecognize.h
    M llvm/include/llvm/Transforms/Utils/BuildLibCalls.h
    M llvm/lib/Transforms/Scalar/LoopIdiomRecognize.cpp
    M llvm/lib/Transforms/Utils/BuildLibCalls.cpp
    A llvm/test/Transforms/LoopIdiom/strlen.ll
    A llvm/test/Transforms/LoopIdiom/wcslen16.ll
    A llvm/test/Transforms/LoopIdiom/wcslen32.ll

  Log Message:
  -----------
  [Transforms] LoopIdiomRecognize recognize strlen and wcslen (#108985)

This PR continues the effort made in
https://discourse.llvm.org/t/rfc-strlen-loop-idiom-recognition-folding/55848
and https://reviews.llvm.org/D83392 and https://reviews.llvm.org/D88460
to extend `LoopIdiomRecognize` to find and replace loops of the form
```c
base = str;
while (*str)
  ++str;
```
and transforming the `strlen` loop idiom into the appropriate `strlen`
and `wcslen` library call which will give a small performance boost if
replaced.
```c
str = base + strlen(base)
len = str - base
```

---------

Co-authored-by: Michael Kruse <github at meinersbur.de>



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